Manoanese-arsenate insecticide of low water solubility



Patented July 22, 1930 V UNITED STATES PATENT OFFICE WILLIAM K. SGHWEITZER, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE GRASSELLI CHEMICAL COMPANY, OFOLEVELAND, OHIO, A CORPORATION OF DELAWARE MANGANESE-ARSENATE INSECTICIDE OF LOW WATER, SOLUBILITY No Drawing.

the availability of such compounds for this purpose.

The water solubility of such arsenicals is usually expressed as per cent. water soluble arsenic acid, AS205, and is determined according to the method given in the Oflicial and Tentative Methods of Analysis of the Association of Agricultural Chemists, paragraphs 12 and 13, page 50, and paragraph 29, page 54, of the 1915 edition. This method consists substantially in the following: A 2-gram sample of the arsenical is digested in 1 liter of freshly boiled distilled water for 24 hours with hourly shaking for 8 of the 24. The test is then filtered and the AS205 determined in the filtrate; the amount so found is referred to as the water soluble arsenic acid.

It the water soluble arsenic acid content of a manganese arsenical containing above a()% AS205 in combined form is about 1% AS205 or more, there is danger of serious burning when it is applied to tender foliage.

I have now found that if, in such a manganese arsenical of sufliciently high arsenic acid content, the water soluble arsenic acid content is reduced substantially below 1% AS205, no

such burning occurs, and I have found a novel manganese arsenate product of high total arsenic acid and low Water soluble As O: content, having powerful insecticidal properties and a process of making the same. In U. S. Patent 1,648,57 7 issued November 8, 1927,H. P. Corson describes a brown colored insecticide which is obtained by acting in presence of a catalyst such as nitric acid with manganese dioxid upon arsenious acid and treating the reaction product with an alkaline agent, such as lime. The manganese arsenate insecticide obtained in this manner is described as containing a total of 42.5% As O and 2.36% water soluble arsenic as I have shown in my U. 8. Patent 1,648,595,

-dated November 8, 1927, that a similar brown colored insecticide can be produced by reacting with manganese dloxid upon arsenlous Application filed December 17, 1927. Serial No. 240,927.

acid in presence of an alkaline agent such as lime. The product probably contains a mixture of various arsenic acid compounds. Made from technical crude materials, it contains between 40 and 50% arsenic acid and 2.5% water soluble arsenic, both expressed as As O My present invention comprises a modification and improvement of said processes as well as the novel insecticide obtained thereby, said insecticide containing arsenates, of manganese as the main active ingredients, but havinga water soluble arsenic acid content substantially below 1% and being exceedingly valuable for treating plant growths.

This novel process consists in effecting the reaction between the manganese dioxid and the arsenious acid under well defined and controlled conditions comprising effective stirring, superatmospheric pressure and temperatures above 100 C. For this purpose an apparatus must be used which will provide good agitation, thorough mixing, and which can be run under a steam pressure of at least 80 lbs. per square inch. It is desirable to provide an apparatus lined with some inert material, as I have found that certain metals, notably iron and steel, considerably slow down the oxidation. Lead is practically inert and can be used in the construction of equipment suitable for this reaction.

Any standard stirring device, if sufficiently efiicient, set up in an autoclave lined with inert material, can be used to advantage in carrying out the reaction. Another convenient apparatus is constituted by a ball mill arranged for heating and withstanding pressures of at least 80 lbs. per square inch. The

charge of arsenious acid and manganese diperatures above 100 0.; the reaction 'proceeds under these conditions without a catalyst at a speed which makes the reaction commercially possible, though catalysts such as nitric acid, nitrobenzene, etc., will further speed up the reaction My novel pressure method applies equally well to the two processes described in the above cited U. S. Patents, Nos. 1,648,577 and 1,648,595. That is to say, I can react with the alkaline agent upon the manganese arsenate as it is formed by the pressure reaction between the manganese dioxid and the arsenious acid or I can produce the manganese arsenate first under pressure and react subsequently thereon with the alkaline agent. The amount of alkaline agent used can vary within wide limits without substantially affecting the result. When using hydrated lime an amount of 10 or more percent. by weight of the combined manganese dioxid and arsenious acid weight is preferred.

In the two-stage process, that is to say, producing the manganese arsenate first and then treating same with the alkaline agent, it is desirable to limit the time of the action of the alkaline agent because prolonged treatment, due probably to some side reac-, tions, increases again the water soluble As O content.

The use of an alkaline agent in this reaction produces several desirable results. It contributes to the-production of an insecticide of low water solubility; it produces a coloration of the finished arsenate ranging from grey to brown, the darkest shades of which make it ver suitable for certain applications, and it a ects the density of the insecticide producing a light fiufiy material of hi h volume. While the reasons for the resuTts obtained b this lime treatment are not fully understoo it is assumed that the alkaline agent reacts with part of the manganese arsenate to form hydrated manganese oxid, which is evenly and intimately distributed throughout the whole reaction product, and an arsenate of the alkaline a cut. It is, therefore, preferred to use an al aline a ent, the arsenates of which are difiicultly so uble in water.

The most easily available alkaline agent which I can use is lime, but others, such as the h droxides of magnesium and barium, have en found to be convenient.

The pressure reaction between the manganese oxid and the arsenious acid is quite rapid. The presence of lime in the one-stage process slows down the speed of reaction without, however, making it commercially prohibitive.

For commercial application of my invention, it is, of course, desirable to make use of a cheap raw material, and I have found that natural manganese dioxid ore, or yrolusite, is very well suited. In this case the fineness of the ore influences the speed of reaction, and it is usually advisable to employ a material the majority of which passes a 100 mesh screen or finer.

The manganese arsenate insecticides obtained by my novel process are grey to brown, light powders. When produced from pyrolusite they contain from 40 to 50% total As-, O and less than 1% water soluble AS205. They are chemically most probably mixtures of manganese arsenates intimately associated with arsenates of the alkaline agent used and more or less hydrated manganese oxid. They have been found to be powerful insectici es and can be applied to tender foliage without any harmful effect.

The following are a few examples of the application of my invention to the productionof'these novel insecticides, but the conditions given therein can be varied within wide limits without departing from the spirit of my invention.

The apparatus used was a lead-lined autoclave containing Danish pebbles and mounted to rotate in a horizontal position. The autoclave was heated directly with gas and through a hollow shaft and flexible coupling connection was made with a pressure gauge. The reaction was carried out at a pressure of to 80 lbs. per square inch. The oxidation of the arsenious acid was checked and the runs carried to obtain complete oxidation. The autoclave was emptied directly on a steam-heated hot late and the product completely dried Di erent types of pyrolusite ore were used. A Java ore contained 16.7% available oxygen and 84.6% passed through a 300 mesh screen. The Caucasian ore contained 16.2% available oxygen and passed entirely through a 200 mesh screen. v Cuban ore contained 15.13% available oxygen and 72.7% passed through a 300 mesh screen.

The followin table shows the condition of reaction an the results obtained; the amounts are given by weight.

Pyrolusite E E {,1 50 3 .2 a u a 1:5 .2 5 G w h s 0,, o '5 g 06 '8 00- a '4 Q g *5 S g 5 g 2 5 g 5 m E o h a 5 a; :3 o is E E s Es .555 2 B c: m B a a a o k 800 Java 800 240 4000 use oxi 4 2 Cream 73 a on 400 Cauca- 400 120 4000 After 010- 4 2 Cream 00 than dltlon 800 Java 800 80 4000 At lplezin- '10 Grey .44

, 11 I 800. Java 800 100 41110 At lgziln 40 Cream .95

In another series of operations on the twostage process, a brick-lined autoclave was used, equipped with the necessary attachments for steam inlet, charging, sampling, measuring pressure, temperatures, etc.

P 1 "t Hairs I w t V yro us: e a i T a er White 80-lbs. 3 soluble arsenic gag to com- A810: (lbs.) plete an (per oxids cent) Grade Lbs. on

161 Java 151 025- 4 s1 40. s es 100 Cuban 110 510 3 5O 41. l 33 '200 Cuban 220 750 2 100 42. 1 23 200 Java 204 750 2 120 l .60

The color in all instances was of a light brown, and the product was found to have very desirable insecticidal properties.

In the two-step process, as exemplified above, I effect the treatment with the alkaline agent under superatmospheric pressure and at temperatures above 100 C. I also found that quite comparable results are obtained when the reaction product of manganese dioxid and arsenious acid as obtained in the first step pressure reaction is subsequently treated with the alkaline a ent at atmospheric pressure and at substantia ly the boiling temperature of water.

I claim: I

1. The process of making a manganese arsenate insecticide which comprises reacting with a manganese dioxid material u bn arsenious acid under steam pressure 0 about 80 lbs. per square inch, and subsequently re acting with an alkaline agent, the arsenates of which are difiicultly soluble in water, upon the manganese arsenates formed.

2. The process of making a manganese arsenate insecticide which comprises eflectin the reaction of a manganese dioxid materia with arsenious acid and an alkaline agent under superatmospheric pressure, at a temperature above 100 C. and under conditions of thorough agitation and mixing.

3. The process of making a manganese arsenate insecticide which comprises reacting with pyrolusite upon arsenious acid in a water slurry at a steam pressure of about 80 lbs. per square inch until the arsenious acid is substantially completely oxidized and subse- 4. As a new. product a manganese arsenate insecticide which has a water soluble AS205 content below 1%, and which comprises manganese arsenates intimate] admixed with the reaction product obtained by treating manganese arsenate, in aqueous slurry, with an alkaline agent, the arsenates of which are difiicultly soluble in water.

5. As a new product amanganese arsenate insecticide which has a water soluble AS205 content below 1%, and which comprises manganese arsenates intimatel admixed with the reaction product obtained by treatin manganese arsenate in aqueous slurry with ydrated lime.

' 6. As a new product a manganese arsenate insecticide characterized by having a water soluble As O content below 1% and which comprises manganese arsenates intimately associated with a diflicultly water soluble earth alkali metal arsenate and more or less hydrated manganese oxid.

7. As a new product a manganese arsenate insecticide characterized by having a water soluble AS205 content below 1%, and which comprises manganese arsenates intimately associated with calcium arsenate and more or less hydrated manganese oxid.

In testimony whereof, I afiix my signature.

WILLIAM K. SCHWEITZER. 

